[GitHub] [servicecomb-java-chassis] wujimin commented on a change in pull request #1789: [SCB-1650]discovery schema from instancies directly

[GitBox]

wujimin commented on a change in pull request #1789:
URL: 
https://github.com/apache/servicecomb-java-chassis/pull/1789#discussion_r431651062



##########
File path: 
foundations/foundation-registry/src/main/java/org/apache/servicecomb/registry/consumer/MicroserviceManager.java
##########
@@ -45,11 +47,21 @@ public MicroserviceManager(AppManager appManager, String 
appId) {
   }
 
   public MicroserviceVersions getOrCreateMicroserviceVersions(String 
microserviceName) {
-    MicroserviceVersions microserviceVersions = 
versionsByName.computeIfAbsent(microserviceName, name -> {
-      MicroserviceVersions instance = new MicroserviceVersions(appManager, 
appId, microserviceName);
-      instance.pullInstances();
-      return instance;
-    });
+    // do not use ConcurrentHashMap computeIfAbsent for versionsByName
+    // because: when create MicroserviceVersions, one creation may depend on 
another
+    // MicroserviceVersions. And pullInstances will create a new 
MicroserviceVersions.
+    // Calling ConcurrentHashMap computeIfAbsent inside will get deadlock.
+    MicroserviceVersions microserviceVersions = 
versionsByName.get(microserviceName);

Review comment:
       hashmap is not thread safe, not only for write, but also for read




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